Development of a universal power management control unit for hybrid ac dc microgrids

Abstract

Renewable energy sources (RES), gaining much importance in establishing a carbon free environment, have led to a phenomenal transformation of existing power grids by introducing the concept of microgrids. Furthermore, microgrids are becoming increasingly important as electric vehicles (EV), and RESs are integrated into the grid. As a result, the loads and generation in the grid are a mix of dc and ac. Hence, the hybrid ac/dc microgrids (HMG) is a promising technology that integrates the benefits of dc and ac technologies. newline newlineThe main aspects of realizing a microgrid are control and stability. However, the lack of inertia of power electronic converters, especially in an islanded HMG, threatens stability and control. Furthermore, the behavior of the system with significant integration of RESs and EV charging stations is also the main concern regarding stability. For these reasons, control and stability analysis have become necessary for implementing HMG. Therefore, a dynamic model of the HMG is developed to carry out the overall stability analysis and to investigate the different control strategies of interlinking converters (IC). newline newlineThe work proposes an adaptive power management strategy that improves the performance of an HMG with a hybrid energy storage system integrated IC. Furthermore, a novel volatile stability index-based droop scheme is implemented to improve the performance of the HMG under volatile loading conditions. The novelty of the proposed controller is the adaptiveness in selecting active power droop gain based on the stability index. The proposed power management strategy is tested in real-time under various volatile conditions to validate the performance. The percentage improvement in voltage profile is 2.68% and 5.55% at the ac and dc subgrid. Finally, a two-level hierarchical controller is implemented to enhance hybrid microgrid operation further. The hierarchical controller is incorporated to reduce the steady-state error, peak overshoot, and settling time. newline